[ticket/11303] add S_TZ_PRESELECT template var

add a new template variable to check if timezone has already been selected
by the user while registeration.

PHPBB3-11303
[ticket/11303] use S_TZ_PRESELECT in subsilver

PHPBB3-11303
[ticket/11303] remove additional brackets

PHPBB3-11303
[ticket/11303] rename attribute to timezone-preselect

PHPBB3-11303
[ticket/11323] Correctly treat variables in template defines

Previously, any template variables that were used when defining a variable
were treated as strings. This is a regression to phpBB 3.0. With this
patch the template variables will be properly parsed.

PHPBB3-11323
[ticket/11323] Enable tests for inclusion of defined variables

PHPBB3-11323
[ticket/11323] Reduce additional code and revert regex to previous one

PHPBB3-11323
[ticket/11383] Correctly revert modules added/removed by migrator

PHPBB3-11383
[ticket/11421] Correctly display submit button when needed

PHPBB3-11421
[ticket/11417] FIx submit button description on notifications options page

PHPBB3-11417
[ticket/11390] Hide pagination when there are no notifications

PHPBB3-11390
[ticket/11390] Correctly separate list of notifications from header

PHPBB3-11390
[ticket/11407] Fix <dfn> description of "notification" option.

PHPBB3-11407
Merge remote-tracking branch 'remotes/nickv/ticket/11407' into develop

# By Joas Schilling
# Via Joas Schilling
* remotes/nickv/ticket/11407:
  [ticket/11407] Fix <dfn> description of "notification" option.
Merge remote-tracking branch 'remotes/nickv/ticket/11390' into develop

# By Joas Schilling
# Via Joas Schilling
* remotes/nickv/ticket/11390:
  [ticket/11390] Correctly separate list of notifications from header
  [ticket/11390] Hide pagination when there are no notifications
Merge remote-tracking branch 'remotes/nickv/ticket/11417' into develop

# By Joas Schilling
# Via Joas Schilling
* remotes/nickv/ticket/11417:
  [ticket/11417] FIx submit button description on notifications options page
Merge remote-tracking branch 'remotes/nickv/ticket/11421' into develop

# By Joas Schilling
# Via Joas Schilling
* remotes/nickv/ticket/11421:
  [ticket/11421] Correctly display submit button when needed
[ticket/11423] Send unformatted usernames to the email template

PHPBB3-11423
Merge remote-tracking branch 'EXreaction/ticket/11423' into develop

# By Nathaniel Guse
# Via Nathaniel Guse
* EXreaction/ticket/11423:
  [ticket/11423] Send unformatted usernames to the email template
Merge remote-tracking branch 'remotes/Blitze/ticket/11383' into develop

# By OpenShift guest
# Via OpenShift guest
* remotes/Blitze/ticket/11383:
  [ticket/11383] Correctly revert modules added/removed by migrator